1. Field of the Invention
The field of the invention is that of digital data broadcasting, notably according to methods that provide for time and frequency interleaving of the data.
Such methods are being developed notably for high quality sound broadcasting applications, especially broadcasting to moving bodies in urban environments, but also to fixed receivers. These applications are often designated by the term DAB (Digital Audio Broadcasting).
The invention can also be applied advantageously in the field of digital television such as for example the DNT (diffusion numerique de terre or earth digital broadcasting) project.
The invention can be applied in particular, but not exclusively, to the broadcasting system known as the COFDM (Coding Orthogonal Frequency Division Multiplex) system as described in the U.S. Pat. No. 4,884,139 published on Nov. 28, 1990.
2. Description of the Prior Art
As a rule, the broadcasting of signals, whether radio or television (analog or digital) signals relies, according to known techniques, on the association of a transmission channel with a specific program. This association is fixed and permanent.
In other words, at present, each television or each radio station is systematically associated with a fixed transmission frequency.
If digital broadcasting is analyzed from the viewpoint of the ISO reference model, the applications, and for example the high quality sound application, correspond to the Presentation layer (layer 6) and Application layer (layer 7). Seen from the other end of the ISO model, the transmission part DAB corresponds to the functions of the Physical layer (layer 1) and the Link layer (layer 2).
It is seen, therefore, that the intermediate layers are not represented. At present, applications and network are closely related. In other words, there is no intermediate protocol that can be used, when possible, to decorrelate an application from the network. While this absence can, in certain cases, facilitate the processing operations, it most usually amounts to a severe handicap.
Furthermore, the extension of this system of broadcasting to other fields of application such as, for example, the broadcasting of personal messages, driving assistance messages, localization messages, television signals etc. proves to be difficult.
The object of the invention notably is to overcome the drawbacks of the prior art.